US Patent 7491926 Offset optical security sensor for a door

A security sensor apparatus senses movement of an object. The sensor apparatus includes an electronics arrangement having an optical emitter and an optical receiver. The optical receiver has an axis of reception. The optical emitter emits a first beam along an axis of emission in an emission direction. The axis of emission diverges in the emission direction from the axis of reception at an angle of at least two degrees. The electronics arrangement is mounted in association a first surface of the object or a second surface of a structure disposed in opposition to the first surface. A reflector arrangement includes at least one reflective surface and is mounted in association with the other of the first surface and the second surface. The at least one reflective surface receives at least a portion of the first beam and produces a second beam directed at and received by the optical receiver.